The present invention relates to a magnetic head slider and a magnetic disk apparatus and, more particularly, to a contact type magnetic disk apparatus in which the magnetic head slider moves relative to a magnetic disk medium while being in contact with it, thus performing recording/reproduction.
In recent years, the recording density increases steadily in the field of information storage files. In the magnetic disk apparatus, to minimize the gap between the magnetic head that writes/reads information and the magnetic disk medium that holds information is one of the elements that are important in increasing the recording density. A so-called contact type magnetic disk apparatus has been developed in which the magnetic head performs recording/reproduction while in sliding contact with the surface of the magnetic disk medium in order to decrease the gap between the magnetic head and the magnetic disk medium. Examples of such a contact type magnetic disk apparatus are described in H. Hamilton, "CONTACT RECORDING ON PERPENDICULAR RIGID MEDIA", Journal of the Magnetics Society of Japan, Vol. 15 Supplement, No. S2, pp. 483-490, 1991 and in WO 93/14495.
In a contact type magnetic disk apparatus of this type, the magnetic disk medium is coated with a lubricant in order to prevent wear and damage to the magnetic disk medium and magnetic head slider caused by contact between the magnetic disk medium and the contact pads of the magnetic head slider.
In this contact type magnetic disk apparatus, since the lubricant on the magnetic disk medium moves to the outer peripheral portion of the medium due to the centrifugal force generated by high-speed rotation of the magnetic disk medium, the thickness of the lubricant decreases on the inner and intermediate peripheral portions of the magnetic disk medium.
In a floating magnetic disk apparatus, when the CSS (Contact Start Stop) method is employed, the magnetic head slider and the magnetic disk medium slide on each other at the start of operation until the magnetic head slider floats from the magnetic disk medium and at the stop of operation until rotation of the magnetic disk medium stops. In this magnetic disk apparatus, the magnetic disk medium is coated with a lubricant, in the same manner as in the contact type magnetic disk apparatus, and a problem concerning depletion of the lubricant arises in the same manner as in the contact type magnetic disk apparatus.
As "a technique for preventing depletion of the lubricant on the magnetic disk medium" concerning the conventional floating magnetic disk apparatus, the carbon protective film containing hydrogen and nitrogen is formed on the magnetic disk medium, and the lubricant to be applied on the protective film is made to have a polar group, so that coupling between the lubricant and the protective film is strengthened, as shown in Japanese Patent Laid-Open No. 6-333231.
As "a technique for preventing depletion of the lubricant on the magnetic disk medium" concerning the conventional contact type magnetic disk apparatus, an integrated head-suspension-wick system is employed in the head suspension so that the lubricant is supplied to the surface of the magnetic disk medium by the capillary phenomenon, as shown in Japanese Patent Laid-Open No. 6-223533.
As another example of "the technique for preventing depletion of the lubricant on the magnetic disk medium", the width of the front end of the contact pad is made larger than that of the rear end thereof to suppress a decrease in the lubricant on the magnetic disk medium under the contact pad, as shown in Japanese Patent Laid Open Nos. 6-12808 and 6-44718.
Japanese Patent Laid-Open No. 7-147070 discloses a magnetic head slider in which the shape of the contact pad is made appropriately in order to suppress a decrease in the lubricant under the contact pad even if a skew angle is formed upon movement of the magnetic head from the inner periphery to the outer periphery of the magnetic disk medium. In this magnetic head slider, the angle of the side surface of the contact pad is made larger than the maximum absolute value of the skew angle. Hence, when the magnetic head slider moves from the inner peripheral side to the outer peripheral side of the magnetic disk medium, the effect of suppressing a decrease in the lubricant is achieved over the entire angular range of the seek operation of the contact pad.
According to Japanese Patent Laid-Open No. 7-147070, the leading edge portion of the contact pad is not parallel to the trailing edge portion thereof. This makes it possible to cause the skewed leading edge portion to provide an extra air-bearing lift at the inner peripheral side of the disk where the local disk speed is low, and a smaller lift at the outer peripheral side of the disk where the air-bearing effect is large because of the higher local disk speed.
As described above, according to the conventional contact type magnetic disk apparatus, since the lubricant on the magnetic disk medium moves to the outer peripheral portion due to the centrifugal force caused by high-speed rotation of the magnetic disk medium, the thickness of the lubricant decreases on the inner and intermediate peripheral portions of the magnetic disk medium, causing wear and damage to the magnetic disk medium and magnetic head slider (contact pad). This problem hinders realization of a high recording density and high reliability of the contact type magnetic disk apparatus.
In order to avoid this problem, the coupling force between the lubricant on the magnetic disk medium and the protective film is increased in the contact type magnetic disk by "the technique for strengthening coupling between the lubricant and the protective film" employed by the CSS type floating magnetic disk apparatus. Nevertheless, wear and damage to the magnetic disk medium and magnetic head slider cannot be prevented due to the following reason. In the contact type magnetic disk apparatus, since the magnetic slider and the magnetic disk medium are always in contact with each other, the lubricant on the magnetic disk medium tends to move easily, and the effect of increasing the coupling force between the lubricant on the magnetic disk medium and the protective film rarely occurs.
The method of supplying the lubricant onto the magnetic disk medium with the wick is difficult to apply to a thin lubricant film having a thickness equal to or smaller than 1 .mu.m, and cannot be applied to a contact type magnetic disk suitable to a high recording density. The reason for this is as follows. If the thickness of the lubricant film is increased, the gap between the magnetic head and the magnetic disk medium increases. Since the recording density largely depends on the distance between the magnetic head and the magnetic disk medium, a high recording density cannot be achieved.
Furthermore, with the shapes of the contact pads disclosed in Japanese Patent Laid-Open Nos. 6-12808, 6-44718, and 7-147070, it is difficult to prevent the lubricant from moving to the outer peripheral portion due to the centrifugal force. This is because with these contact pad shapes the lubricant cannot be moved from the outer peripheral portion to the inner peripheral portion of the magnetic disk medium.